Sleep Calculator

Calculate ideal bedtimes and wake times based on 90-minute sleep cycles.

What Is a Sleep Calculator?

Find the best bedtime and wake-up time based on 90-minute sleep cycles.

Wake up refreshed, not groggy, by timing your sleep to complete full cycles.

How to Use the Sleep Calculator

Follow these steps:

  • Choose whether you want to calculate a bedtime or a wake-up time.
  • Enter your desired wake-up time or bedtime.
  • Click calculate to see the best sleep times.
  • Pick a time that allows 5-6 complete cycles.

Tips

  • Aim for 7.5-9 hours of sleep (5-6 cycles).
  • Keep a consistent sleep schedule.
  • Create a relaxing bedtime routine.

Frequently Asked Questions

What is a sleep cycle?+
A sleep cycle lasts about 90 minutes and moves through light, deep, and REM sleep. Waking between cycles (rather than during deep sleep) helps you feel more refreshed. Most adults need 5-6 complete cycles (7.5-9 hours).
Why do I feel groggy after 8 hours of sleep?+
You may be waking during deep sleep. Try adjusting your alarm by 15-30 minutes. Aim for complete 90-minute cycles, so 7.5 hours (5 cycles) may feel better than 8 hours.
How long does it take to fall asleep?+
The average person takes about 10-20 minutes to fall asleep. This calculator uses 15 minutes. Adjust your bedtime accordingly if you fall asleep faster or slower.

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Sleep Calculator — free online sleep calculator, sleep cycle calculator, bedtime calculator, wake up calculator, sleep cycles. No signup required. Works in your browser.